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Battery Energy Storage Solution Power the Futhure

VRLA Battery General Knowledge


 What’s VRLA battery 

A battery is an electricity storage device which can be found in any number of shapes, size, voltage and capacities.

When two conducting materials (often dissimilar metals) are immersed in a solution, an electrical potential will exist between them is connected together through a closed circuit, a current will flow. The value of this potential (or voltage) is dependent on the materials used, giving rise to a whole family of battery types each having benefits and restrictions in use. Examples are: – lead acid, nickel cadmium ( NiCad ), lithium, silver alkaline.

This manual is concerned only with one battery technology, the most successful «Lead Acid battery» (lead and lead oxide immersed in sulphuric acid). Each cell has a 2 volt potential.

The Lead-acid Battery

A battery is simply a number of cells connected together with a given voltage and capacity. The more cells the higher the voltage, the large the plates the higher the capacity (in general).

Purely for convenience, batteries are made in 12 volt blocks with 6 cells but are also available in 6 volt, 4 volt and even 2 volt, single cell blocks.

Batteries can be connected in series to achieve whatever voltage is required (add the number of 2 volt cells) and in parallel to achieve the capacity required (add the capacities of each parallel battery or string of batteries) . For larger systems, a number of series connected strings maybe connected in parallel with each other. This achieves both a higher voltage and capacity.

Two Concepts Three basic applications
  1. Sealed or Regulated Lead Acid VRAL
  2. Open-Vented
  1. Sealed or Regulated Lead Acid VRAL
  2. Automotive (starter i.e. Cars, commercial vehicles)
  3. Open-Vented
VRLA has in many instances replaced the open-vented type.

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 The Lead-acid Battery 

There are two concepts in lead-acid batteries and three basic applications.

Two Concepts Three basic applications
  1. Sealed or Regulated Lead Acid VRAL
  2. Open-Vented
  1. Sealed or Regulated Lead Acid VRAL
  2. Automotive (starter i.e. Cars, commercial vehicles)
  3. Open-Vented
VRLA has in many instances replaced the open-vented type.

This guide is focused on Industrial Standby applications and NOT Automotive or Traction use.

Industrial Batteries
Industrial batteries are available from two distinct groups with the following features. Note: VRLA have superseded open-vented in many applications

  1. Older technology
  2. Require separated battery room
  3. Regular routine maintenance
  4. Separate safety requirements
  5. Store/use in vertical position
  6. Can require extensive cabling
  1. Environmentally friendly
  2. Use directly in office environment
  3. Low maintenance-”maintenance free”
  4. Self-contained. Safe
  5. Store/use in any orientation
  6. Can be used internal or adjacent to load
VRLA has in many instances replaced the open-vented type.

Note: The term sealed lead-acid SLA is an old acronym Considered misleading and is now replaced by Valve Regulated Lead Acid VRLA.

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 Typical VRLA battery applications 

Typical Applications

It is vitally important to define your priority before size of battery. These include:
High rate performance/Long life-unattended/High cycle life/Cost effectiveness

Telecom Communication UtilityUPS Marine Cable TelevisionAlarm system Security Equipment

Medical Equipment Electronic Test Equipment

Portable Television & Video Equipment

Power Tools Solar Power Lighting

Toy Vehicles Wheelchair Golf Trolleys

Semi-traction Lawn Mowers Lifting Equipment


To optimize battery duty and life for your application, make sure you choose the right product from the BSB range.

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How to choose the right size of battery
As mentioned earlier, batteries come in all shapes and size, from types no larger than a shirt button, to a battery system filling an entire room.
To find the size of battery you require you generally need two pieces of information, battery load and back-up times. (Note: other factors may also have an effect).

Battery Load
Whether you power lights, motors, electronic equipment or a toy vehicle you equipment will draw a load in AMPS. If this is unknown then the equipment will have a rating expressed in Watts which may simply be converted to Amps by dividing the value by the normal voltage of the system.

Back-up Time
This is the time you require the battery to support the load described above and is often called Autonomy or discharge time.
Example: To power a cordless electric tool for a total of 3.0 hours before recharging. With these two pieces of information use our selection graph to plot an intersection point from which you will determine a required size or capacity in Amp. hours (Ah).

Our figure has been rationalized into rounded figures of capacity. If your intersection point falls between two lines choose the next highest value.

Always choose a suitable sized battery from the ranges appropriate to your application.

You may notice that the chosen capacity in Amp hours is often higher than the Value of Amps x Hours used, in our example using 10AMPS x 3 HRS = 30Ah and the chosen option being 38 Ah. This is because the capacity of each NP battery is stated at the 20 hour discharge rate. You will only get full capacity if discharged over that length of time.

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Correct charging of a VRLA battery is essential in optimizing battery performance and life. Although a constant voltage charge should be applied, optimum charging also depends on temperature (Nominally 20 degree), charge current (max 1/4 battery capacity) and ripple current (minimum) . Two basic categories of charging exist.

To find the size of battery you require you generally need two pieces of information, battery load and back-up times. (Note: other factors may also have an effect).

This charging method is used in applications such as emergency back-up when the battery is required only upon mains failure e.g., continuously on charge and consequently the recommended voltages are slightly lower than cyclic charging so as not to damage the battery.

Cyclic charging is used in applications where the battery is repeatedly discharged then charged, e.g. Portable equipment, Wheel Chairs, Golf trolleys etc.
A higher charging voltage is used but should NEVER be left on indefinitely since is will overcharge and destroy the battery.

Note: For optimum performance always recharge a battery immediately after discharging. Consult the individual battery specification for the correct charging voltage or contact BSB Technical Department

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The Storage or shelf life of a VRLA battery is usually between 12 and 18 months at 20 degree starting From a charged condition.
Warning :
Never store in a discharged or partially discharged state.
Always store in a dry, clean, cool environment in a fully packaged condition.
If storage of 12 months or longer is required supplementary charging will be require

Design Life
Float Each battery type will be have a prescribed float design life. Please be aware of this life expectancy and replace the battery as End-of-life approaches. Keep a reference or lable the battery to show its date of installation to facilitate replacement at the correct time. Factors other than time may affect the life of the battery and this will be indicated by a reduction in capacity. The battery should be required duty. This may be well in advance of its design life if, for example, the ambient temperature is considerably above 20 degree ie 30 degree or more.
Cyclic Each battery suited to cyclic use will reach End-of-life after a prescribed number of cycles. This number is dependant upon the depth of discharge of each cycle. The deeper the discharge, the less number of cycles to End-of-life. Depth of discharge is expressed as the percentage of the battery capacity required per duty cycle.

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Battery Care
Each BSB VRLA battery is supplied I a charged condition having passed stringent quality checks.To ensure optimum battery performance and life, it helps to take care of your battery by observing the following:

Warning – Never leave a VRLA Battery in a discharged state.
If a battery has an open-circuit voltage lower than its rated value, then sulphation may well be the cause.
When a battery is left a discharged state or for prolonged periods of storage, lead sulphate crystals begin to form acting as a barrier to recharge and will prevent normal battery operation.
Depending on the degree of sulphation, battery may be recovered from this condition by constant current charging at a higher voltage with the current limited to one tenth of the battery capacity for a maximum of 12 hours.

Note: The applied voltage will exceed the normal recommendation and so the battery must be monitored (not left unattended) and removed from charge if excess heat is dissipated. The voltage required to «force» this maximum current into the battery will reduce as the battery recovers until normal charging can take place.

In extreme circumstances a battery may never fully recover from sulphation and must therefore be replaced.

As mentioned in Section 4 optimum charging relies mainly on voltage, current and temperature factors which are interrelated and all of which can cause overcharge.
Excessive charge voltages will force a high overcharge current into the battery, which will dissipate as heat, and may cause gas emission through the safety valve. Within a short period of time this will corrode the positive plate material and accelerate the battery towards end-of-life.

Under these conditions the heat produced inside the battery can lead to thermal runaway due to the increased electrochemical reaction within the battery. The battery may swell before failing and will be irrecoverable from this state. This situation is potentially dangerous.

Warning – Heat Kills Batteries.
The recommended normal operating temperature is 20°C.
HIGH TEMPERATURE will reduce battery service life often quite dramatically. In extreme cases this can cause Thermal Runaway, resulting in high oxygen/hydrogen gas production and battery swelling. Batteries are irrecoverable from this condition and should be replaced.

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In order to ensure the safe operation of our BSB VRLA batteries, correct and accurate procedures must be employed. Please read the below document thoroughly and retain it for reference in case it is needed in an emergency situation.
All individuals who work with VRLA must be made aware of the Dangers, Warnings, Attentions and Suggestions, for proper use of our batteries in order to avoid accidents and injuries.

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  • Do not seal the battery inside of any machinery. Please make sure that the battery is well ventilated. Placing the battery in an hermetically sealed space can cause the battery to explode causing damage to the machinery or extreme personal injury.
  • Do not place the battery in a hermetically sealed space that is closed or close to any source of heat or flame. This could cause the battery to ignite or even explode. All connection cables should be well insulated and not able to short electrically. If the cables do cause an electrical short, that may cause smoke or the battery to cause a large destructive fire.
  • Do not use any metal such as steel wire brush to connect or clean the terminals. Be careful not to drop any personal jewelry, hair pins or any other metallic objects when servicing the batteries. Metal objects can cause an electrical short which can be a source of leaking, heat or a destructive fire.
  • Do not use any metal such as steel wire brush to connect or clean the terminals. Be careful not to drop any personal jewelry, hair pins or any other metallic objects when servicing the batteries. Metal objects can cause an electrical short which can be a source of leaking, heat or a destructive fire.


  • Always use the proper charger and the charging regulations set by BSB. Not following our guidelines and procedures, or using non-approved charging procedures, can cause the battery to leak acid, heat up, or cause a destructive fire.
  • When our batteries are used for medical applications, please be aware of the possibility that the battery could fail. Back-up units should be in place to prevent injuries.
  • The container cannot come in contact with metal products. Please use insulated material that has acid and heat resisting characteristics to be the battery container. Not using insulated materials may cause fire or an explosion by leaking.
  • Do not install batteries close to any location where a spark may occur such as a switch or a fuse. Sparks may cause fire or an explosion.
  • Always wear insulated gloves during any battery servicing activities, otherwise you could get an electrical shock.
  • Do not install a battery in a high traffic area without adequately protecting the battery. Not doing so could cause an electrical shock or fire in case the battery is disturbed or dislodged.
  • Do not burn the battery or throw it into a fire. Doing so may cause the battery to explode and toxic gas to be released.
  • Do not disassemble, reassemble or destroy the battery. Doing so could cause the acid inside the battery to leak and cause severe burns or other accidents.
  • Do not use any dry fabric or other materials to clean the battery that could cause static electricity. Always use a damp cloth that has had the moisture wrung out of it.
  • The battery should be replaced before the expiration date. Upon installation a log of expiration dates should be kept in a handbook or on front of the machinery.
  • When the battery’s performance has only 50% left at 25°C, the battery should be replaced. The battery’s life will curtail one half with a raise of each 10°C in temperature. If the discharging current is higher than 0.25CA, the battery’s life will be shorted.
  • When the battery approaches the end of its life, its performance will decrease very fast. The internal exhausted electrolyte and the corrosion of the positive plate may cause a failure. If the battery continues in operation under these conditions, there could be extreme heat, leaking of even explosion.
  • There is sulfuric acid inside of the battery. Please use water if skin or clothes become contaminated by the acid. If acid gets into your eyes, use ample clean fresh water to flush your eyes and seek immediate medical attention.

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  • The standard operating temperature for our batteries is 5-35°C (41-95°F). Usage outside this range will cause damage to the battery.
  • Our batteries cannot be used beside any heat source such as a transformer.
  • Do not let water or sea water wet or soak our batteries.
  • Do not leave one of our batteries inside an automobile or any other place with strong sunlight.
  • Do not place our batteries in areas where there is a lot of powder residue. The powder could cause a short in the battery.
  • When using our batteries in a series, connections should be made between the batteries before charging or placing the series under a load. Remember, the positive terminal of the battery must connect to the positive side of the charger or the load. The negative terminal of the battery must connect to the negative side of the charge or load. Otherwise an explosion may occur causing personnel or equipment damage.
  • Be careful when handling batteries or taking them out of their racks or storage units. Please wear protective footwear when handling our batteries.
  • When unpacking BSB VRLA batteries from their shipping container, be careful when removing them so as not to drop them. If dropped, their container could crack and cause sulfuric acid to leak out.
  • Placing BSB VRLA batteries upside down could cause sulfuric acid to leak out.
  • Do not grab the battery terminal or cable to shift its position. Doing so could cause damage to the battery or electrical shock.
  • Be careful not to let a battery fall. A dropped battery could cause a crack in its container and sulfuric acid could leak out.
  • Some of the models of our batteries are very heavy, please carry or transport them correctly to prevent an occupational injury.
  • Please do not use any type of organic solvent to clean our batteries.
  • Always release any static electricity buildup on your body before touching or servicing our batteries to prevent sparks.
  • Do not use plastic sheets to cover our batteries. Removing a plastic sheet could cause a static electricity build up and sparks could occur.
  • Please use the connection screws that BSB provides to avoid possible sparks.
  • Please use insulated materials to cover the terminal and connector in order to avoid possible sparks and shorts.
  • For electric mobility, bikes or lawn mowers where the equipment might have vibrations during usage, please be sure that our batteries are firmly anchored to avoid damage or shorting of the terminals.
  • Please terminate all switches between the battery, load or charger before making any connections.
  • Do not use the battery out of its application usage range. Doing so may cause leaking, heat or fire.
  • If there is an observed unusual situation of charging voltage or discharge characteristics, please replace the battery.
  • Please follow the list below to ensure proper battery safety. A failure to do so could cause a battery to leak, radiate heat or cause an explosion.
  • Ensure that there is a correct connection between the battery and the charger; do not reverse the terminal connection.
  • Do not weld directly on the terminal.
  • Do not mix different brands, models, or date codes of batteries.
  • Do not dismantle any part of the battery assembly.
  • Do not throw the battery or hit it with any type of instrument.
  • Do not charge the battery over the recommended charging time, otherwise the battery could leak, radiate heat, or even explode.
  • Our batteries should be placed in a safe place out of reach from children. If our batteries are the power source for a toy that a child uses, they should be supervised and instructed in the proper operation, charging and usage of the battery
  • BSB VRLA batteries are constructed with a negative plate absorption system. This means the oxygen from the positive plate will be absorbed by the negative plate. In the first 12 months of usage, the float charge voltage may be out of the standard value. This is normal for this type of battery.
  • If there is an unexpected electrolyte (sulfuric acid) spill or leakage, immediately neutralize the spill with sodium carbonate then wipe it up. If the spill is not neutralized, there could be corrosion on the floor or equipment.
  • If a battery catches on fire, please use a proper powder charged fire extinguisher. Do not ever use a water based fire extinguisher.
  • After an earthquake, please check the tightness or each connection to avoid spark.
  • After an earthquake, please inspect each battery container to make sure that there are no cracks or leaks. If you notice an unusual situation, immediately terminate the operation of the equipment to ensure the safety of all personnel and equipment.

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  • Please make sure that the battery is properly stabilized. A strong impact can affect the battery’s performance.
  • Battery life should be verified by actual loading conditions as well as by different charging/discharging conditions.
  • Battery installation should only be done by trained and qualified personnel.
  • For the initial use or if a battery has been stored for a long period of time, please recharge the battery fully before putting it into service. A battery’s performance will reduce automatically by self discharge.
  • If a battery is stored for more than 3 months, we suggest a recharge before the battery is put into service. When storing a VRLA battery, a recharge should be repeated every 3 months.
  • Do not let a VRLA battery discharge to a voltage lower than its suggested final voltage. Doing so will affect the battery’s performance.
  • Do not over-discharge a VRLA battery. After discharge immediately recharge a battery.
  • Use the right charging/discharging settings to ensure the battery’s quality and performance.
  • Shut down the main switch of any equipment that the VRLA battery is connected to after usage otherwise an over discharge state may occur.
  • If the equipment will not be in use for a long period, please remove the battery from the equipment and store in a dry area.
  • If the environmental temperature increases by 10°C, the recharging time must be decreased by one half. If a battery is stored under 35°C, it should be recharged every 11/2 months instead of every 3 months.
  • If a battery is stored for more than a year without any recharging activity, the battery’s life will be worth less than the original specifications.
  • VRLA battery inventories should be rotated to ensure that batteries pulled out of storage are fresh and ready to use. After a long period of storage, without a regular recharging program, a battery’s performance may not come back to specified capacity.

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Finally, when a battery has reached the end-of-life it must be returned to the point of sale or to a licensed battery dealer for recycling. Please observe the following points.

Do not throw batteries in a bin at end-of-life. VRLA batteries contain substances harmful to the environment so return to your supplier or take to your Council tip for disposal.
Never bury in the ground or incinerate at end-of-life. Batteries contain harmful substances making this unsafe.

Either return ‘spent’ battery:

  • to your stockist
  • to your local council tip
  • to a licensed ‘spent’ battery dealer

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VRLA -Valve regulated lead acid battery.
SLA -Sealed Lead-acid
CCV -Closed – circuit voltage.
OCV -Open – circuit voltage
WPC -Watts per cell.
Pb -Chemical symbol for lead.
UPS -Uninterruptible power supply
Ah -Amp hour. The unit of battery capacity
DOM -Date of manufacture.
EOD -End of discharge.
VPC -Volts per cell.
Nc -Number of cells.
Vf -Float voltage.
Vs -Starting voltage.
Iav -Average current.
Sg -Specific gravity
cAn -Is the defined capacity of the battery to the Time period.
20hr Rate -The capacity a battery will deliver over 20hrs


A Plastic material largely used for the case and cover of batteries.

The substance which electrochemically reacts in the electrode of batteries. Lead-acid batteries adopt lead dioxide for the positive electrode and spongy lead for the negative electrode.

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Average temperature in the vicinity of the battery.

The capacity actually available from a cell/battery. The available capacity is the capacity when it discharges at a specified hour rate, and expressed in hour rate and Ah.

A type of battery terminals, to which lead wires are connected with bolts.

The built-in thermostat is a reset table switch built in a battery for temporarily cut off the battery circuit when the temperature of the battery exceeds a preset values or when the battery charge/discharge at a higher rate than predetermined.

The electric capability of a battery. It usually means ampere-hour capacity expressed in Ah or C(coulomb).

The minimum battery unit which composes a storage battery. Nominal voltage of the cell of the lead-acid battery is 2V.

The operation of supplying a battery with a DC current from an external power source to have the electrode active material conduct chemical reactions then to store electric energy as chemical energy in the battery.

Test of batteries to check whether or not they are adequately recharged after discharge.

General term for ampere-hour efficiency and watt-hour eficiency. In many cases, however,it means the ampere-hour efficiency.

A method of charging: to charge a battery with a constant current.

A charge or discharge current rate expressed in A or mA.It is numberically the same as the hour rate capacity of a battery expressed in Ah of the rated capacity.

The terminal voltage of a battery at which discharging should be discharging should be discontinued. This voltage depends on discharge current, type of electrodes and construction of battery.

The number of charge/discharge/rest cycles a cell/battery can provide. Cycle life is usually expressed by the number of cycles available before duation of discharge decreases to a half of the initial value.

A value to express the state of discharge of a battery. The depth of discharge is generally expressed by the ratio of discharge amount to rated capacity of the battery.

To draw off the electric energy stored in a cell/battery.

The term to express the magnitude of discharge current. When assuming discharge current and time to discharge cut-off voltage t hours, this discgarge is called t-hour rate(tHR) discharge, and the current is called t-hour rate diacharge current. When time t is minutes instead of hours, tMR is used.

Test of batteries in ordinary use including charge, discharge and rest.

The medium which serves to conduct ions in the electrochemical reactions in batteries. The lead-acid battery adopts diluted sulfuric as the electrolyte.

Energy available per unit Approx. mass or unit volume of a cell/battery. Energy desity is expressed in Wh/kg or Wh/l.

The system in which a constant voltage is continuously applied to a battery connected to a rectifier in parallel with a load to maintain the battery in charged state: on occurrence of power failure or load variation, the battery supplies power to the load without any short break.

Capability of a battery to recombine (or absorb) internally generated oxygen gas at the negative plate. The greater this capability is, the larger the available charge current.

A very rapid discharge of a battery. (in many cases it means discharging at approx.1 CA or higher rate.)

The pressure within a sealed battery. Internal pressure of a battery is increased by oxygen gas which is generated from the positive plate at the end of charging.

The resistance within a battery; it is the total of individual resistances of the electrolyte and the positive and negative plate. Internal resistance is simply measured with the current four-terminal method(1,000Hz) and expressed in the composite value of resistance component and capacitor component.

Touching of the positive and negative plates within a call.

The time period until a cell/battery loses its expected characteristics.

Low maintenance means that no watering norequalizing charge is requireed in operating batteries.

A circuitry designed to discontinue discharge of a battery at a predetermined voltage level.

The matallic pieces which are attached to a SLA battery as the terminals.

A phenomenon where a temporary drop of discharge voltage is observed during deep discharge of an alkaline rechargeable battery which has been subjected to shallow charge/discharge. Cycles or trickle charging over long time.

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The battery electrode into which a current from the external circuit flows during discharging. The negative plate has lower electric potential than the positive plate to the electrolyte. The negative plate is incorporated with connection parts such as the electrode pole.

A nominal value of capacity of a cell/battery, which is a measure of electric capability. Rated capacity is rather approximate compared with rated capacity.

A nominal value to indicate the voltage of a cell battery. Generally, nominal voltage value of a battery is somewhat lower than its electromotive force. Nominal voltage of the lead-acid battery is 2.0 V per unit cell.

Measured voltage of a cell/battery which is electrically disconnected from the external circuit.

Continuted charging of a fully charged cell/battery. With batteries which require watering, overcharge causes electrolysis of water, resulting in rapid decrease of electrolyte. Generally, overcharge adversely influences battery life.

Discharge of a battery to a voltage below a predetermined cut-off voltage.

Simultanous charging of two or more batteries connected in parallel. In cyclic use of batteries, specifically, the parallel charge tends to cause an imbalance in charge state among the batteries, which may shorten their service life.

A plastic material which is often used for the case and cover of batteries.

The battery electrode from which a current flows to the external circuit during discharging. The positive plate has higher electric potential than the negative plate to the electrolyte. The positive plate is incorporated with connection parts such as the electrode pole.

Charging in a short time with a large current.

The stated capacity of a battery; namely, the ampere-hour amount can be drawn from the battery in fully charged state at a specified temperature, at a specified discharge rate, and to a specified cut-off voltage. The symbole CN may be used to express the rated capacity of N-hour rate.

The rechargeable battery is a system comprising two different electrodes and ion-conductive medium, whi